This invention relates generally to an apparatus for detecting whether a weld nut is properly oriented while being resistance welded to a workpiece.
Weld nuts are often used in applications where the nut portion of a nut and bolt fastening arrangement is inaccessible after completed assembly of a production article. For example, weld nuts are often used in hollow automobile cross members to facilitate bolting to the cross member. Once the cross member is assembled, the weld nut is inside of the hollow member and is inaccessible. If the weld nut were welded upside down to the interior surface of the cross member, the entire cross member may have to be discarded or, preferably, recycled, because the weld nut is inaccessible and unserviceable.
To reduce the probability of assembling articles with upside down weld nuts, manufacturers often use a method of inspecting the weld nuts. One method of inspecting the weld nuts is to use an automated visual inspection system. This method is often expensive to put in place, and requires computer programming to accommodate parts with different appearances and profiles. Another method of inspecting the weld nuts is to employ an inspector who is assigned the task of making sure the weld nuts are properly oriented. While this method generally produces satisfactory results in the inspection process, it can be costly and subject to human error.
Accordingly, one aspect of this invention is to provide a relatively simple and reliable method of determining whether a misoriented weld nut has been welded to a workpiece.
Another aspect of this invention is to provide a weld electrode that cooperates with a weld nut in such a way that the electrical properties of the weld event are substantially different between properly oriented and misoriented weld nuts.
Yet another aspect of this invention is to provide an inexpensive method of reliably and automatically determining whether a weld nut is properly oriented.
In accordance with these aspects, the present invention provides a weld nut electrode for differentiating between a properly and an improperly oriented weld nut. The electrode has a conductive portion for passing weld current through the weld nut and an insulated portion electrically isolated from the conductive portion. The conductive portion makes electrical contact with a properly oriented weld nut and the insulated portion makes exclusive contact with an improperly oriented weld nut. Sensing of the conductive or nonconductive condition can provide an indication as to nut orientation.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.